Tobacco use constitutes the single most preventable cause of disease and death in the world today and is responsible for introducing a number of diseases including many types of cancer, cardiovascular diseases, and respiratory diseases. In the United States alone one in every five deaths is smoking related, which translates to an estimated $157 billion in health-related economic losses each year. Impairment in sexual functioning has also been reported as sequelae of long-term tobacco intake. Extensive literature indicates that cigarette smoking is an independent risk factor for introducing erectile impairment in men, and that chronic smokers are approximately 1.5 to 2 times as likely as nonsmokers to report erectile dysfunction. The primary aim of the study is to provide the first empirical investigation of both the acute and intermediate effects of smoking cessation on physiological and subjective measures of sexual function in men who are experiencing erectile impairments. Smoking participants (N=100) will be tested 4 times;at baseline while smoking ad lib, during the first week of nicotine transdermal patch treatment (21 mg), 24 hours after patch cessation, and 8 weeks after patch cessation. Participants will use the nicotine patch for 8 weeks in a step-down fashion (21 mg daily for 4 weeks;14 mg daily for 2 weeks;7 mg daily for 2 weeks). During each visit, sexual functioning will be assessed via rigorous psycho-physiological techniques (penile plethysmography to measure erectile capacity) and by self-report measures (sexual arousal, sexual desire, and sexual satisfaction). Sex hormones (testosterone) and in vivo nicotine concentration levels will additionally be assessed during each visit. The sexual functioning of smokers will be compared to matched, nonsmoking controls (N=30) in order to ascertain whether men who smoke regain a similar profile to nonsmokers with respect to biological, physiological, and subjective aspects of sexual function. The present study adopts a translational research approach in the hope that these findings may have the potential for facilitating programs and interventions targeting the prevention and cessation of cigarette smoking in men. We therefore believe that the aims of the present study will help further the mission of the National Institute for Drug Abuse's (NIDA) Behavioral and Integrative Treatment Branch (BITB), within the Division of Clinical Neuroscience and Behavioral Research (DCNBR).